dna structure

Question 1

what is DNA?

Answer 1

1. contains all the information needed to build an organism
2. provides the instructions for making proteins in cells

Question 2

what are nucleotides?

Answer 2

1. monomers of DNA polymer
2. made up of a deoxyribose sugar (5 carbon sugar molecule), phosphate group and a nitrogen base.
3. the carbon atoms are numbered 1’ to 5’. the 5’ carbon is attached to the phosphate group and the deoxyribose sugar while the 1’ carbon is attached to the nitrogenous base and the deoxyribose sugar

Question 3

what are the four nitrogen bases?

Answer 3

adenine (A), thymine (T), guanine (G), cytosine (C).
nitrogen bases are classified into two groups; pyrimidines and purines.
- pyrimidines are made up of one ring, thymine (T) and cytosine (C)
- purines are made up of two rings,
adenine (A), and guanine (G)

Question 4

what is the genetic code?

Answer 4

the specific order of bases

Question 5

what is condensation polymerisation?

Answer 5

• joins together nucleotide monomers of DNA
• a phosphodiester bond, a strong covalent bond, is formed between the oxygen ion of the phosphate group of one nucleotide and the OH group on the 3’ carbon of the sugar molecule.
• nucleotides bond together to form the sugar-phosphate backbone of the DNA molecule, the 5’ carbon end of the chain has a free phosphate group, while the 3’ carbon end has a free OH group.
• two strands of DNA are antiparallel; one strand runs from 5’ to 1’ (phosphate to sugar) and the other runs 3’ to 5’ (sugar to phosphate).

Question 6

what is the complementary base pairing rule?

Answer 6

1. only a purine pairs with a pyrimidine
2. adenine pairs with thymine, guanine pairs with cytosine.
3. the percentage of adenine in a cell must be equal to that of thymine, and the percentage of guanine must be equal to that of cytosine.
4. complementary base pairs are joined by hydrogen bonds, double H bond between A and T, triple H bond between G and C.

Question 7

what forms the DNA’s 3D double helix shape?

Answer 7

• the sugar-phosphate backbone are the sides of the ladder, the bonded complementary nitrogen bases form the rungs. other intermolecular forces cause the whole structure to twist into a spiral

Question 8

how is DNA stored in eukaryotes?

Answer 8

1. DNA folds and wraps around proteins called histones
2. this forms a DNA-histone complex, or chromatin
3. chromatin supercoils and loops which causes the structure to become thicker, which forms the chromosome.
4. two chromatids are joined at the centromere.